There is considerable interest regarding the formation of carbon-carbon bonds via olefin metathesis. Olefin metathesis (or disproportionation) refers to the metal-catalysed redistribution of carbon-carbon double bonds. Cross metathesis (CM) can be described as a metathesis reaction between two non-cyclic olefins, which may be the same or different, for example:

Where the olefins are the same, the reaction is known as self metathesis.
Ring-opening metathesis polymerization (ROMP) is a variant of olefin metathesis reactions wherein cyclic olefins (for example) produce polymers and co-polymers, for example:

Ring-closing metathesis (RCM) represents a process in which an acyclic diene (for example) is cyclised to produce a cycloalkene, for example;

As indicated above metathesis reactions take place in the presence of a catalyst. A great deal of research has been done in an attempt to synthesise and isolate catalysts which are able to catalyse homogeneous olefin metathesis reactions. More particularly the synthesis of Group VIII transition metal metathesis catalysts has lead to catalysts with increased functional group tolerance and stability with respect to conditions such as air, water and acids.
During the 1990's the so-called “1st generation Grubbs catalyst” of formula 1a was developed:
where Cy is cyclohexyl.
This well defined ruthenium (Ru) alkylidene catalyst afforded high selectivities, high reaction rates and good tolerance for oxygenates in feed during homogeneous olefin metathesis reactions, including cross metathesis, ring closing metathesis and ring opening metathesis polymerisation. These processes have many potential commercial applications for the commodities, pharmaceutical and fine chemicals industries as well as in the field of speciality polymers. Several reviews describe the development and applications of Grubbs-type catalysts (for example Acc. Chem. Res. 2001, 34, 18–24; Angew. Chem., Int. Ed., 2000, 39, 3012–3043).
Much research has been carried out to investigate the effect of changing the nature of the ligands, (for example J. Am. Chem. Soc. 1997, 119, 3887–3897; Tetrahedron Lett. 1999, 40, 2247–2250; Angew. Chem., Int. Ed. 1998, 37, 2490–2493) resulting in the development of second generation Grubbs catalysts. The main thrust of second generation Grubbs catalyst research has related to a move away from the use of phosphine ligands to the use of highly nucleophilic N-heterocyclic carbenes for homogeneous metathesis reactions. Formula 1b shows the structure of the standard second generation Grubbs catalyst. While this catalyst shows greater reactivity compared to catalyst 1a, it is more expensive than the first generation catalyst.
                where Cy=cyclohexyl and Mes=mesityl        
In the case of hydroformylation reactions, research has continued into the use of phosphine ligands. It will be appreciated that in a hydroformylation process an olefinic feedstock is reacted with carbon monoxide and hydrogen at elevated temperatures and pressures in the presence of a hydroformylation catalyst to produce oxygenated products. The hydroformylation catalyst is selected according to the particular oxygenated products which are required from a particular olefinic feedstock and may typically be phosphine and/or phosphite ligand modified rhodium (Rh) or cobalt (Co) catalyst. Many different phosphine and phosphite ligands have been suggested in the past. For example U.S. Pat. No. 3,400,163 discloses bicyclic heterocyclic sec- and tert-phosphines of the general formula 1c and it is stated that these phosphines are useful in the hydroformylation of olefins.

U.S. Pat. No. 3,420,898 discloses olefin hydroformylation reactions in the presence of a cobalt catalysts with phosphine ligand of formula 1c.
Research has indicated that those phosphine ligands which appeared to lead to catalysts with higher selectivities and reaction rates In homogeneous metathesis reactions were often not suitable for the types of catalysts used in hydroformylation reactions, for example HCo(CO)3P where P represents a phosphine ligand, for example tricyclohexyl phosphine (PCy3).
However, it has now surprisingly been found that certain relatively inexpensive (compared to second generation Grubbs catalysts) phosphorus containing ligands such as phosphabicylononane ligands, which have been used in hydroformylation reactions, provide excellent stability, product yields and selectivities when used in a homogeneous metathesis catalyst. In addition, it has surprisingly been found that metathesis catalysts incorporating these phosphorus containing ligands in at least some cases show enhanced resistance to feed impurities. Furthermore, in at least some cases these catalysts afford superior performance for ring closing metathesis, ring opening metathesis polymerization and cross metathesis when compared to the standard first generation Grubbs catalyst (1a). When compared to the rather expensive standard second generation Grubbs catalyst (1b), in at least some cases their activity is comparable while the reaction selectivity is often superior.